I have stood on Hadrian's Wall looking at the long view northwards, with the wind in my face and deep sympathy in my heart for those poor Roman legionaries. I have watched herds of red deer come down to the road to feed less than a mile from hundreds of skiers taking advantage of a late cold snap by making a day trip to the slopes. I have had my best-ever cream tea in a thick mist on Exmoor after failing to see a single marsh fritillary butterfly all day. All these, and many other delights, have happened to me in a national park.There is almost certainly a national park near you. Most of us live within an hour of at least one huge area of iconic countryside – conserved and protected from most development and with a legal obligation to "promote opportunities for [your] enjoyment". Off-road cycling, craft shopping, natural history expeditions, surfing, historic ruins, village fetes and, of course, walking are all available.
These parks are not there by accident. In 1949 the National Parks and Access to the Countryside Act was passed. It was a small but significant piece of legislation from Clement Attlee's radical postwar Labour government. It created a legal framework for the present-day national parks, and specified relative ease of access: "The distribution of selected areas should as far as practicable be such that at least one of them is quickly accessible from each of the main centres of population."
By 1957 there were 10 national parks, and another five have been added since. The most recent addition was the South Downs national park in March 2010.
They were a long time coming. In 1882, after a legal and political battle, the mayor and the City of London Corporation opened Epping Forest with the commitment that the conservators should "at all times keep Epping Forest unenclosed and unbuilt on as an open space for the recreation and enjoyment of the people". This was a brand new idea: a large area, whose primary function was to provide recreation space for people who did not live in it. It was also Britain's first "nature reserve". Epping became a forerunner of the national parks idea. It was badly needed.
Through the 19th century, Britain experienced an unprecedented period of social change. The population increased – from 9.4 million in England and Wales in 1801 to 32 million a century later. And this expanded population had substantially relocated. The majority of the people switched in barely three generations from rural peasants to industrial labourers living in slums. A new sense of "ownership" led to access becoming more limited; not only were a growing number of people crammed in to cities, but the places they could escape to were increasingly restricted and infringements punitively dealt with.
At the same time, romanticism exalted the freedom and beauty of wild terrains. In his Guide to the Lakes (expanded edition, 1835) Wordsworth claimed Cumbria as "a sort of national property, in which every man has a right and interest who has an eye to perceive and a heart to enjoy". The desire and love for untamed nature increased just as the access to it was being aggressively denied.
Not surprisingly, Epping Forest was a success: on a single day in 1920, it welcomed 102,000 visitors. But not every city had an Epping Forest. After the first world war the demand for a "right to roam" grew steadily, with particular resentment at the way people were being excluded by landowners in favour of grouse shooting. In 1932 the escalating frustration, especially among radicalised industrial workers in Manchester, led to an organised mass trespass on Kinder Scout in the Peak District, which has been described by Roy Hattersley as "the most successful direct action in British history". Gradually, recognition that access to the wilder parts of the UK had to be widened grew, and the creation of the national parks was a direct response.
An excellent treatment for sulking teenagers, by the way, is to take them up to Kinder Scout, along the beautiful new, rugged gritstone path and tell them the story: they especially like the bit where the gamekeepers get beaten up.
The 15 UK national parks now cover 8,748 square miles – almost 10% of England and 20% of Wales, though less of Scotland (just over 7%). Until this century there were no national parks in Scotland, mainly because access has always been more open so there was less need for them. Soon after devolution in 1998, two parks were created (Cairngorms and Loch Lomond and the Trossachs), with a focus on sustainable development. There is a proposed third park on the west coast: a maritime national park.
Last year nearly 80 million people visited the parks. The UK population is about 63 million, and only 7% of the visitors came from abroad, so many people must have visited more than once. Core funding for parks comes from the devolved governments, which together provide about £75m (less than £1 per visitor). Given their role in conservation and the preservation of extensive reaches of beautiful countryside, their contribution to rural employment and the pleasure and health benefits they provide to visitors, this is a bargain.
Last year I visited Inchmahome, an island in the Loch Lomond and the Trossachs national park. The ruins of the hidden 14th-century priory were magically tranquil and I could not help thinking that my £1 had made this joyful visit possible: without national park funding there would not have been a ferry to take me across the water.
Nonetheless, our national parks are something of an anomaly. None of them fits into the International Union for Conservation of Nature (IUCN) definition of a national park – among other considerations the state does not own or control the land in the UK's national parks: almost all of it is owned by a patchwork of individuals or by local councils and charitable or conservation organisations such as the National Trust.
The IUCN definition requires national governments to have "taken steps to prevent or eliminate exploitation or occupation as soon as possible in the whole area", but all our national parks have permanent residents. In some cases rather a lot of them: 120,000 in the South Downs. All of them contain settlements, in certain instances quite substantial towns, and these bring all the infrastructural development ("exploitation") that modern life requires. In short, they are not chunks of untouched wilderness. They are far more domesticated: allocated areas with specific and restricted planning regulations. Each is managed by a separate park authority that wields considerable power in pursuit of its two statutory objectives: "to conserve and enhance the natural beauty, wildlife and cultural heritage of the area" and "to promote opportunities for the understanding and enjoyment of the special qualities of national parks by the public".
The national parks all wrestle with challenges and threats. The most obvious are: the tensions between visitors and local inhabitants desiring further development; the problems of degradation and erosion of the land itself; and the conflict between conserving the freedom of the wild places and making them accessible, safe and comprehensible for people who have grown up without any experience of such places.
The coalition government, having cut the national parks' core grant by nearly a quarter in the cause of austerity, has just announced that it is providing over £16m to further its cycling agenda. This is centralisation of power, where spending decisions could have been left to the individual park authorities. But overall the national parks should be seen as a marvellous success. There are moves to expand both the Peak District and the North York Moors parks. Visitor numbers and wider public awareness continue to rise. There are good grounds for celebration.
Get out there. If you have children, get them out there. Try a new one if you already know some of them. As Arthur Hobhouse wrote in his 1947 legislative proposals: "There is merit in variety, and with the wide diversity of landscape which is available, it would be wrong to confine [your] selection of national parks to the more rugged areas of mountain and moorland, and to exclude other districts which, though of less outstanding grandeur and wildness, have their own distinctive beauty."
To each their own, but I have scared myself on a fungi walk, learning about toadstools in Ballochbuie forest, where the ancient pine trees creak and moan; I have got myself mildly lost on Dartmoor and become convinced that the hound of the Baskervilles was lurking in the gloaming; I have watched the geese coming down at dusk on to the salt marshes in Norfolk; I have recaptured a childhood joy sailing a Laser dinghy on Kielder Water. And I have walked in the wild places of Britain and been filled with joy.
Sara Maitland is a novelist and short-story writer. Her latest book, Gossip from the Forest, is out now. To order a copy for £7.99 with free UK p&p call 0330 333 6846 or go to guardianbookshop.co.uk